1. Field of the Invention
The embodiments discussed herein are directed to a method and apparatus for allocating a connection identifier (CID) in a wireless communication system, such as a WiMAX system, and particularly to a technique for allocating a CID for reducing time until the establishment of call connection.
2. Description of the Related Art
WiMAX (Worldwide Interoperability for Microwave Access) is a communication connection standard. WiMAX is used for the so-called last one mile and the like in an area where the laying of a broadband line is difficult. WiMAX is also a standard of a wireless communication technology that is expected to be used as a communication connection standard for high speed mobile communication. WiMAX is intended for wireless communication covering a medium and long distance area in a range of several km to several tens of km. WiMAX is technology that forms a MAN (Metropolitan Area Network) exceeding a LAN (local area network).
The standardization of WiMAX is promoted by the IEEE 802.16 Working Group and WiMAX Forum, an industry organization, to ensure interconnectivity between different equipment.
In the WiMAX standard, BS connection management part 1401-2 in BS 1401 and MS connection management part 1402-2 in MS 1402 execute a communication connection establishment control operation, as shown in FIG. 14, while the BS transmission and reception part 1401-1 in the base station (hereinafter referred to as “BS”) 1401 and the MS transmission and reception part 1402-1 in the mobile station (hereinafter referred to as “MS”) 1402, which is a portable terminal, perform wireless communication.
At this time, BS 1401 and MS 1402 exchange and determine an identifier called a connection identifier (hereinafter referred to as “CID”) with each other. BS 1401 and MS 1402 also perform user data communication using this determined CID.
FIG. 15 is an operation sequence diagram showing procedures until a CID is allocated and user data flows between BS 1401 and MS 1402 shown in FIG. 14 in the WiMAX standard.
First, the channel scan procedure of operation S1501 is carried out. In this procedure, the operations of downstream channel complement and synchronization establishment are executed. MS connection management part 1402-2 searches for WiMAX wireless signals from BS 1401 and receives messages of DCD (Downlink Channel Descriptor), UCD (Uplink Channel Descriptor), DL-MAP (Downlink Map), and UL-MAP (Uplink Map), in which information on the channel is written, according to this procedure.
Next, the initial ranging procedure of operation S1502 is carried out. In this procedure, first, MS 1402 sends a ranging code message to BS 1401. In response to this, timing adjustment information, output adjustment information, frequency adjustment information, and the like are transmitted from BS 1401 to MS 1402 in order that BS 1401 continuously receives a signal from MS 1402. Next, MS 1402 sends a RNG-REQ message to BS 1401. In response to this, BS connection management part 1401-2 allocates to MS 1402 a basic connection ID (hereinafter referred to as “basic CID”) and a primary connection ID (hereinafter referred to as “primary CID”). The basic connection ID and the primary connection ID are used for the subsequent message exchange, using a RNG-RSP message. The BS connection management part 1401-2 simultaneously records these CIDs in a connection identifier database (hereinafter referred to as “CID-DB”) 1401-3 (FIG. 14). After this, message exchange between BS 1401 and MS 1402 is carried out using a fixed CID in each procedure until the transport connection establishment procedure of operation S1505. The fixed CID is the above-described basic CID or primary CID.
Next, the basic capability procedure of operation S1503 is carried out. In this procedure, MS connection management part 1402-2 transmits the basic function of MS 1402 to BS 1401, using a SBC-REQ message. Then, BS connection management part 1401-2 transmits a function common to BS 1401 and MS 1402 to MS 1402, using a SBC-RSP message.
Subsequently, the authentication/encryption procedure of operation S1504 is carried out. In this procedure, a control operation in which BS 1401 authenticates MS 1402 is carried out. Specifically, MS connection management part 1402-2 transmits an authentication request to BS 1401 using an AuthRequest message. In response to this, BS connection management part 1401-2 carries out the authentication of MS 1402. If the authentication is successful, BS connection management part 1401-2 transmits an authentication key to MS 1402, using an AuthReply message.
Next, the registration procedure of operation S1505 is carried out. In this procedure, network parameters are determined between BS 1401 and MS 1402 using a REG-REQ message that is transmitted from MS connection management part 1402-2 to BS 1401, and a REG-RSP message that is transmitted, in response to this, from BS connection management part 1401-2 to MS 1402.
Subsequently, the transport connection procedure of operation S1506 is carried out. In this procedure, MS connection management part 1402-2 or BS connection management part 1401-2 requests of MS 1402 or BS 1401 the setting of a service flow. The service flow setting is a pass for performing data communication using a DSA-REQ message. The BS connection management part 1401-2 or MS connection management part 1402-2 that receives the DSA-REQ message responds using a DSA-RSP message and establishes a service flow. At this time, BS connection management part 1401-2 selects an unused CID by performing an inquiry to CID-DB 1401-3. The BS connection management part 1401-2 then transmits the CID as a transport connection ID (hereinafter referred to as “transport CID”) for user data transfer, with service flow parameters, to MS 1402, using a DSA-RSP message. Also, BS connection management part 1401-2 records information on the allocation of the transport CID in CID-DB 1401-3.
When MS 1402 first starts data transmission using this transport CID, the bandwidth allocation procedure of operation S1507 is carried out. In this procedure, a request for the allocation of a bandwidth for data transmission is performed by MS 1402 to BS 1401. MS connection management part 1402-2 performs bandwidth ranging and requests of BS 1401 the allocation of a bandwidth for transmitting a bandwidth request message for notifying a necessary bandwidth. By reflecting the result of this request in a UL-MAP message, BS connection management part 1401-2 allocates to MS 1402 a bandwidth for transmitting a bandwidth request message. By transmitting a bandwidth request message using this allocated bandwidth, MS connection management part 1402-2 performs a request for a bandwidth necessary for the upstream line to BS 1401. BS connection management part 1401-2 transmits the result of this request to MS 1402, using an UL-MAP message.
Subsequently, MS 1402 transmits and receives user data to and from BS 1401 using the transport CID. Upstream user data from MS 1402 to BS 1401 is transmitted using a bandwidth determined by the above-described UL-MAP message.
In this manner, in the conventional WiMAX standard, user data communication is started with many procedures as described above. In urgent communication, on the other hand, such as an emergency call, there is a strong desire to omit sequences as much as possible to reduce time until connection and to start communication immediately.
Also, the Ministry of Land, Infrastructure and Transport, and the National Police Agency promote ITS (Intelligent Transport Systems) in which road traffic problems, such as a traffic accident jam, are solved by networking people, roads, and vehicles with information using leading-edge information communication technology. When WiMAX wireless communication is applied to the communication technology for ITS, BS-MS communication should be performed within a limited service area and for a short time because the moving speed of a vehicle in which an MS is mounted is fast. Particularly, information on safety (the notification of the risk of an intersection accident, and the like) should be instantaneously transmitted.
However, in the above-described conventional art, a CID is determined on the BS side and transmitted to the MS, so that time is required for the exchange.
A technique described in Japanese Laid-Open Patent Publication No. 2006-526308 is a technique in which a BS broadcasts uplink channel information (UL-MAP) including one or more CIDs to an MS. The MS selects a CID randomly for a connection request and transmits a connection request message to the BS. But, this technique is not a technique for selecting a transport CID for user data transmission.
Also, a technique described in Japanese Laid-Open Patent Publication No. 2001-53675 is a technique in which a BS allocates and transmits an unused CID for user data transmission to an MS. But, in this technique, the BS performs allocation determination, so that time for notifying the allocated CID from the BS to the MS is required.